1. Field of the Invention
This invention relates to a titanium-containing PET copolyester excellent in heat resistance and transparency, particularly the titanium-containing PET copolyester suitable for manufacturing injection molded bottle preform having weight greater than 600 grams and thickness greater than 7.0 millimeters as well as an injection stretch blow molded refillable container having an inner volume of greater than 10 litters and capable of being returnable and refillable up to 20 loops of returning.
2. Description of Prior Art
As the public pay more attention to the quality of drinking water, many public places of company usually prepare distilled water contained in 5-gallon container for people to drink. Therefore, bulk water market is expanding gradually.
At present, this sort of bulk water container is mainly made from polycarbonate (PC). However, PC containers have been reduced in use gradually due to containing bisphenol-A harmful to human health as well as production costs generally more expensive.
A polyester represented by a polyethylene terephthalate (PET) is excellent in mechanical strength, chemical stability, gas barrier properties, hygienic properties, etc., is available at a relatively low cost and is light in weight, and thereby has been widely used as various packaging materials as e.g. bottles and films, or as fibers, etc. Such a polyester has been produced mainly by employing an antimony compound as a polycondensation catalyst.
And, a copolyester normally containing 0-3 mole % of isophthalic acid based on the copolyester or 1.5-4.0 mole % of diethylene glycol based on the copolyester is characterized in being easy to crystallize during inject-stretch-blow-molding process, so that such copolyester is only suitable to manufacture a thick-walled PET bottle preform having a thickness of about 3-4 millimeter and a weight of only about 100-120 grams maximum and a thick-walled PET bottle or container having an inner volume less than 5 litters. On the contrary, if the same copolyester is processed to manufacture a thick-walled PET bottle preform having a thickness of about over 7 millimeter and a weight of over 600 grams, a situation of crystalline haze unavoidably occurs to the manufactured bottle.
As a result, a PET bottle preform having crystalline haze occurred shall further cause a successive injection blowing process for producing a thick-walled PET bottle is then unstable; on the other hand, a cooling time needed to cool the produced bottle preform must be extended in order to prevent a situation of crystalline haze occurred on the bottle, while the cooling time if extended shall cause the PET bottle to be manufactured in lower productivity and economical invalidity.
For solving the aforementioned problem, U.S. Pat. No. 6,309,718 discloses a polyester composition for manufacturing a large molded polyester container weighing greater than about 200 grams and having an inner volume of several gallons. The polyester composition contains 4-10 mole % of cyclohexane dimethanol or 6-17 mole % of isophthalic acid or combination of the above both compounds; and, dicarboxylic acid compound such as naphthalene-2,6-dicarboxylic acid having a content of 50 mole % maximum is further added as a component of the polyester composition; the intrinsic viscosity of the copolyester is 0.75-0.85 dl/g.
For improving those polyesters or copolyesters mentioned above, the applicant had been granted an U.S. Pat. No. 6,913,806 which invented and disclosed a copolyester composition containing polyethylene terephthalate (PET) suitable to manufacture a thick-walled bottle preform having a weight of over 600 grams and a thickness of over 7.0 millimeter and a thick-walled container having an inner volume of over 10 litters, the main component of the copolyester composition being polyethylene terephthalate resin, the copolyester composition further containing X mole % of isophthalic acid based on the copolyester, Y mole % of diethylene glycol based on the copolyester, Z mole % of 2,6-naphthalene dicarboxylic acid based on the copolyester, wherein X, Y, Z conforming to the following conditions:2.5≦X≦6.0;2.5≦Y≦5.0;0≦Z≦5.0;the intrinsic viscosity of the copolyester is between 0.75 and 0.85 dl/g.
The commercial PET bottles having an inner volume of over 10 litters offered for sale on the market is usually a kind of returnable and refillable containers capable of refill after being returned and washed. The maximum loops of returning the commercial PET bottle capable of being returned, washed and refilled to maintain aesthetic and functional viability is about 15 loops, and the PET bottle shall be broken, cracked or deformed after over 15 loops of being returnable and refillable.
The commercial PET bottle if cracked or deformed normally is chopped into a small pieces of flakes and melted in higher melting temperature for recycling. But, since global warming and climate change is worsening day by day, it is a great urgency to effectively develop green energy technology to the surroundings for saving energy and reducing carbon.